JPS625333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern position detection device used in a reduction projection type mask aligner or the like.

For example, a conventional pattern position detection device such as a reduction projection type mask aligner is configured as shown in FIG. That is, the circuit pattern 3c of the reticle 3
is precisely aligned with the circuit pattern on the pellet 1a of the wafer 1, which has been exposed and patterned in the previous step, and then irradiated with the exposure light source 31 consisting of a mercury lamp 28, an interference filter 27, and condenser lenses 25 and 26. It is necessary to irradiate the exposed light through a condenser lens 5, project it in a reduced size through a projection lens 4, and print it onto the pellet 1a of the wafer 1. Note that 29 is an exposure system. For this reason, a method is used in which the positional deviation between the alignment pattern 3b on the reticle 3 and the alignment pattern 1b on the pellet 1a is automatically detected using the detection system 30, and the wafer stage 2 is corrected by the amount of this deviation.

The reticle 3 is previously aligned with the lens barrel for absolute conversion using the reticle mark 3a. The monochromatic light emitted from the wafer illumination fiber 15 passes through the semi-transmissive mirror 10, the objective lens 6, the mirror 7, the transparent part (window) of the alignment pattern 3b, passes through the projection lens 4, and is reflected by the wafer alignment pattern 1b. , passes through the projection lens 4, mirror 7, objective lens 6, relay lens 11, and mirror 12 again, passes through the V-shaped slits 22a and 22b, and the condenser lens 23, and reaches the photoelectric conversion element 24.

Further, the monochromatic light emitted from the reticle illumination fiber 14 passes through the condenser lens 13, the mirror 9, and the mirror 8, is reflected by the reticle alignment pattern 3b, and passes through the mirror 7 and the objective lens 6. With this illumination, the reticle alignment pattern 3 is created as shown in Figure 2.
Around the V-shaped window in b (consisting of chrome deposited part)
becomes bright and can be clearly distinguished from the peripheral part of the wafer alignment pattern 1b, which is imaged on the transparent part of the V-shaped window.

The slit scanning section 30a is connected to the bearing guide 1.
8, a photoelectric scale (detection means for detecting the scanning amount of the slit) 19 fixed to the scanning plate 22, a lamp 20 and a lens 21 used for illuminating the photoelectric scale 19, and a scanning plate 22. It consists of upper V-shaped slits 22a and 22b, a galvan 16 for driving the scanning plate 22, and a lever 17.

Since the superimposed image of the alignment patterns 1b and 3b is focused on the scanning plate 22 by the objective lens 6 and the relay lens 11, the slits 22a and 22b are
By continuously moving and scanning in the X direction from the state shown in FIG. 2B, FIG. 2C, FIG. 2D, and FIG. 2E from the state shown in FIG. As shown in F, the position of the edge of the window of the alignment pattern 3b and the wafer pattern 1b is detected by the brightness signal.

Next, based on FIG. 3, reticle pattern 3b is
A method for extracting the positional deviation of the wafer pattern 1b will be explained. That is, by the above-mentioned reticle illumination, the edges C, D, A of the window of the reticle pattern 3b,
B becomes brighter and can be distinguished from the peripheral area of wafer pattern 1b. The positions of C, D, A, and B are determined as the maximum points (deviation points) of the differential value of this detection signal 32. Further, the left and right pattern center positions Wr and We of the wafer pattern 1b are determined as the positions where the symmetry of the signals at the periphery of each step pattern 1b having a line width of 6 μm is the best. If the center position C+D/2 of the right window 3b is calculated and ΔXr=C+D/2−Wr is calculated, this becomes the positional shift amount of the right pattern. Similarly, on the left side, ΔXe=A+B/2−We. From this, the deviation amounts Δx and Δy of the patterns 1b and 3b in the x and y directions are expressed by the following equations.

△x=△Xr+△Xe/2, △y=△Xr−△Xe/
2 As shown in FIGS. 2A to 2E, when one slit 22a scans the patterns 3b and 1b, the other slit 22a scans the bright part of the chrome-deposited part of the reticle 3b, so that the photoelectric conversion element 24 The light from both slits 22a is added and detected. In general, the photoelectric conversion element 24 such as a photomultiplier tube exhibits a characteristic that noise increases as the light level increases, so the S/N ratio of the obtained detection signal is significantly reduced due to the excess light from the other slit 22a. , has the disadvantage of lowering the detection accuracy of patterns 1b and 3b. Moreover, when the alignment pattern 3b is a linear pattern as shown in FIG.
Although not affected by reticle illumination, since the area around the alignment pattern 3b is transparent, if there is a foreign object 35 around the wafer pattern 1b, the slit 22
When the slits 22a and 22b scan and move, the slits 22a and 22b
The brightness from 22b becomes discontinuous, causing disturbance in the detection signal output from the photoelectric conversion element 24 as shown in FIG.
This method has the disadvantage of significantly reducing We detection accuracy.

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
It is an object of the present invention to provide a pattern position detection device which can obtain a detection signal with a good S/N ratio and perform highly accurate position detection.

That is, in the present invention, the slits are provided with light plates on both sides of the pattern, and while one slit is scanning the pattern, the other slit is scanning over the edges and the light plate.
It is characterized by being configured to block excess light from the other slit and significantly improve the S/N ratio of the detection signal obtained from the photoelectric conversion element, thereby detecting the position of the pattern with high precision. be.

The present invention will be specifically described below based on embodiments shown in the drawings. FIG. 6 is a block diagram showing an embodiment of the pattern position detection device of the present invention. That is, 3
3 is a V-shaped slit 2 formed in the scanning plate 22;
This light shielding plate has a V-shaped cutout 34 of a size suitable for the arrangement of the slit scanning portion 30a and the light shielding plate 22b, and is fixedly installed above the scanning plate 22 of the slit scanning unit 30a. (The state seen from above is as shown in FIG. 7.) The rest of the structure is the same as in FIG. 1. However, when the galvan 16 is activated and the scanning plate 22 is reciprocated and scanned by the lever 17, the output level of the video signal detected from the photoelectric conversion element 24 is reduced to about half as shown in FIG. In the D-A section, the light is blocked by the light shielding plate 33 and changes to a low level, but the S/N ratio is significantly improved.
In particular, when compared with the conventional video signal shown in FIG. 2F, the remarkableness of this effect is clear. Furthermore, when the light shielding plate 33 is installed, foreign objects 3 are removed as shown in FIG.
5, the optical image of this foreign object 35 is covered, so this influence can be eliminated and disturbances in the video signal can also be prevented.

In the above embodiment, the light shielding plate 33 is fixedly installed above the scanning plate 22, but it may be installed anywhere on the optical axis connecting the alignment pattern 3b on the reticle 3 to the condenser lens 23.

As explained above, according to the present invention, the S/N ratio is improved and the detection accuracy is not affected by foreign matter, making it possible to obtain a detection accuracy of 0.1 μm (converted on the wafer surface).

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a conventional pattern position detection device used in a reduction projection mask aligner, etc., and FIGS. 2A to 2E show the relationship between patterns and slits in the device shown in FIG. Figure 2F is a diagram showing the video signal waveform detected by the photoelectric conversion element in the device shown in Figure 1;
The figure is a diagram for explaining the method of detecting the position of a pattern in the apparatus shown in Figure 1, and Figure 4 is a diagram for explaining the method for detecting the position of a pattern in the
A diagram showing a case where a linear pattern is used as a reticle alignment pattern in the apparatus shown in the figure, and a foreign object is present. Figure 5 is a video signal waveform detected by a photoelectric conversion element by scanning the pattern shown in Figure 4. FIG. 6 is a schematic configuration diagram showing an embodiment of the pattern position detection device according to the present invention, FIG. 7 is a plan view of the light shielding plate shown in FIG.
The figure shows a video signal waveform detected by the photoelectric conversion system in the apparatus shown in FIGS. 6 and 7. Explanation of symbols, 1b...Pattern, 3b...Pattern, 19...Photoelectric scale, 22...Scanning plate, 22a, 22b...V-shaped slit, 24...
...Photoelectric conversion element, 33... Light shielding plate.

Claims (1)

[Claims] 1 A pair of window-like slits are formed facing in the same direction as the above-mentioned direction so that images of at least one pair of linear patterns facing in intersecting directions pass through, and reciprocating scanning is performed in one direction in which the window-like slits are arranged. A detection means is provided for detecting the scanning amount of the slit, and the slit is scanned back and forth, and when the image of the one linear pattern is passed through the window-like slit, the other window-like slit is In order to block the passing light image, fixed position shielding plates are provided at both scanning ends of the window-like slit, and a pair of light shielding plates are provided at both scanning ends of the window-like slit, and a pair of light-shielding plates are scanned back and forth through the slit to pass through each window-like slit that is not blocked by the light shielding plate. A condenser lens is provided to condense an image of a linear pattern, and a photoelectric conversion element is provided to receive the image condensed by the condenser lens and convert it into a video signal, and a video signal obtained from the photoelectric conversion element is provided. and a scanning amount of the slit detected by the detection means to detect the position of the pattern.